Means for dressing threaded abrasive wheels



P 1949- F. A. LOHUTKO MEANS FOR DRESSING THREADED ABRASIVE WHEELS '2 Sheets-Shet 1 Filed Dec. 4, 1946 n lllllll ll lllll lIlllIHlIlIl Sept 27, 1949; F. A. LOHUTKO 2,482,784 I MEANS FOR DRESSING THREADED ABRASIVE WHEELS Filed Dec. 4, 194a 2 Sheets-Sheet 2 IN V EN TOR.

Patented Sept. 27, 1949 MEANS FOR DRESSING THREADED ABRASIVE WHEELS Floryan A. Lohutko, Detroit, Mich., assignor, by mesne' assignments, to 'Niles-BementPond Company, West Hartford, Conn, a corporation of NewJersey Application December 4, 1946, "Serial No. 714,026

4 Claims. 1

This invention relates tea novel process and means for the dressing of threaded abrasive wheels, such as are intended for the fiDlSh'fOIlliing of- -the teethof gears, and has for its object to-provide for the finish dressing of such abrasive wheel by means which will obtain extreme accuracy of thread form to meet the particular gr-inding requirements of the finally dressed wheel.

ll/lore particularly, the invention proposes to provide means forthe process of finish dressing of the-thread of a helicoidal abrasive wheel, such means being in the nature 01 a free cutting irusto-conical tool, such as of diamond impregnated carboloy or similar material, arranged to rotate on an axis perpendicular to the axis of the abrasive wheel and to be fed across the face o'f the wheel at a speedcommensurate with the lead'of said thread while the abrasive wheel and the dressing tool are both being rotated about their respective axes.

Still further objects oradvantages additional or subsidiary to the aforesaid objects, or resulting from the construction or operation of the invention as it may be carried into efiect, will become apparent as the said invention is herematter further disclosed.

=In carrying the said invention into effect, I may utilize the novel arrangement of elements hereinafter described, by way of example, having reference to the accompanying drawings, wherein:

Figure -1 is a somewhat schematic elevation of a mechanism for the profiling of an abrasive gear grinding wheel by means of a crusher roll and its finished dressing by means of a frustoconical'dressing toolin accordance with the novel process the precise proportions of the elements of the structure as shown being departed "from or exaggerated for purposes of clear and simple illustration;

Figure 2 is a partial sectional elevation showing't'he relationship of abrasive wheel and crusher roll taken on a plane indicated by the line 22 in Figure 1;

Figure 3 is a similar view showing the relationship-between the conical dressing tool and the abrasive wheel taken on a plane indicated by .the vline 3--3 in Figure 1; v

Figure 4 is a front elevation of the crusher roll and dressing tool together with their mountings;

and

Figure 5 is a side elevation of the elements shown-in Figuree,

Similar characters of reference indic'atesimilar parts in the several figures of the drawings.

Referring first to Figure 1 of the drawings; Iii indicates an abrasive wheel, such as may be intended for the grinding orforming ofiteeth :on a spur wheel blank, the said abrasive'wheeli heing characterised by its having formed on its periphery a thread 1'! which -is in CIOSS-iSECtiDIl conjugate to the rack form of the gear 'to be ground; and the present invention relates to the means of forming this thread ion the peripheryof the abrasive wheel. 7

For such purposes I utilize an annularly ribbed crushing roll l2 havinga rib toirib spacing, which is equivalent to the circular pitch of the gear which the abrasive wheel is eventually intended to grind.

The abrasive wheel. island the crusher roll. l2 :are intended'to have relatively reciprocal]motion imparted thereto, and, in the present example, such reciprocation is confined to -the abrasive wheel although .as :a matter of -.design :it -.could be imparted to the crusherroll to producethesame resu t :as will :be well understood; and it .is desired that throughout the present description :andin, interpreting the claims thattheutilization of 'the terms reciprocating theabrasive wheel be 'considered in such, broad sense as to embrace the 'obvious alternative of the reciprocation of the pressure rollrelative to the abrasive wheel.

The abrasive wheel is is shown as being mountedfor rotation on and .by'the shaft 14 which is splinechas at l5, for longitudinal slid- .ing connection with a driving coupling i6,;.th e latter being in turn driven by the bevel gear 11 of ald-ifferential which includespinions l8 and a further meshing lbevelygear l:9

20 is a driving motor, preferably of the variable speed type, operating a driving pinion 2| which meshes :with ring gear 22 of the said differential, .this ring gear also meshing with the first of a train-,of change speed gears (23, 24, 2.5, :26 and 21. The saidgear21 drives a feed screwl28 whichvis threaded into the arm 29 of a bracket 30 secured .to-the said shaft M, This bracket '30 is provided with suitably adjustable stops 3! and 32 posi- Ztioned for-the timedyoperation of a reversing switch 33 for-efiecting thereversing-of the drive motor -2llas said switch is operated by 0118*01311 other'of saidistops.

:34- is -a shaft through which rotation of the gear 19 of the difierential :may'be efiected from any suitable source, as by a belt 135, to control the speed.-ofrrotationrof the shaft i l-relative to that of the driving motor to =meet special circumstances; but this is not an essential part of the present invention which relates to the dressing operation only and need not be discussed in any further detail herein. For the purposes of this description, the gear 19 may be considered as fixed.

It will be apparent that by means of the gearing described and the operation of the feed screw 28 thereby, the abrasive wheel [0 may be caused to reciprocate, say, to the extent indicated by the dotted lines in Figure 1, while it is at the same time being rotated, and that, as this reciprocation is reversed by the operation of the reversing switch 33 in any conventional manner, the direction of rotation of the abrasive wheel will at the same time be reversed; so that any stationary point presented to the surface of the grinding wheel during such operation thereof will traverse a helical path thereon and retrace the same path in the opposite direction upon reversal of the motions described.

As a section of the threaded abrasive wheel taken on a plane at right angles to the lead of the thread is comparable in all its elements to a rack of the gear to be ground thereby, the crosssectional form of the ribs of the crusher roll are accordingly in counterpart of such rack. Thus the crusher roll, when applied to the abrasive wheel in the manner illustrated with requisite feed-in adjustment toward the axis of the wheel and relative longitudinal feed, in the illustrated example, of the abrasive wheel to conform with the lead of the thread or threads to be formed thereon, will crush the thread form including the top of the thread, and also crush the root of the thread somewhat below the depth to which it is to be finally dressed.

The present invention relates to the means and process of effecting this final dressing of the abrasive wheel thread after crushing and also to the combination of such means with provision for its setting relative to the crusher roll as will be now further described.

The crusher roll !2 is shown as being mounted for adjustment and operation in a fixture, as shown in Figures 4 and 5, which includes a frame structure 54 carrying a slide 55 which is adjustable by micrometer feed 35 toward and from the axis of the abrasive wheel ill. The front end of the said slide carries a bracket 31 on which the crusher roll I2 is mounted for free rotation, this bracket being pivoted at 38 for swinging about an axis passing transversely through the axes of the crusher roll l2 and the abrasive wheel It]. It is preferred that this pin 3!; be so located that its axis passes directly through one of the ribs of the crusher roll as shown in the said Figures 4 and 5.

39 are locking screws for securing the bracket 35 in positions of angular adjustment about the axis of the said pin 38. The purpose of this angular adjustment is to secure the required setting angle of the crusher roll I2 relative to the axis of the abrasive wheel is as dictated by the helix angle of the thread to be crushed into the peripheral surface of the said abrasive wheel.

Also mounted on the top of the slide 35 and adjustable thereon by the micrometer feed 40 is a supplementary slide 41 carrying the vertical adjustable bracket 42; 43 being the micrometer device for determining such vertical adjustment. This bracket 42 is provided with a bearing member 44 in which the spindle 45 of a dressing tool 46 is mounted with the axis of the said spindle radial to the axis of the abrasive wheel l0. By

means of the micrometer adjustment 43 the axis of the said spindle 45 may also be adjusted so that it will be spaced from the ribs of the crusher roll to an extent whereby it will occupy a position which would be that of one of the said ribs if the crusher roll were extended to that point. In other words, if, following the crushing of a thread by the roll on the periphery of the abrasive wheel in the manner understood, the axial feed of the abrasive wheel be continued in the required direction until it passes in front of the said spindle 45, then the axis of the said spindle would trace a true path along the root of the thread.

The dressing tool 45 is in the form of a pencil having a conical or frusto-conical cutting end which may be of diamond impregnated carboloy, the angle of the cone corresponding to the thread angle to be dressed on the wheel, so that when the cone end of the dressing tool is brought to the proper dressing depth by the means provided it has line contact with both oblique sides of the previously crushed thread. There is no necessity of providing different setting angles when using this form of conical dressing tool for different helix angles of threads such as are required when disk crushing tools or grinding wheels are used for such final dressing operation.

During a dressing operation, the grinding wheel is given relatively slow rotation while the pencil dressing tool is rotated at high speed, as by means of the motor 41 mounted on a slide 42 and coupled to the spindle 45 by means of the belt 48. The free-cutting dressing tool will thus finish the sides of the threads in the abrasive wheel removing tooth tip and tooth flank errors that may have developed on the thread form during the initial crushing operation.

It will be observed that the dressing operation described may be effected, upon completion of the crushing operation by the crusher roll l2, by simply continuing the advance of the axial feed of the abrasive wheel until the pencil type dressing tool referred to traces the path of the root of the crushed thread by reason of the relative positioning of the dressing tool to the crusher roll in the manner hereinbefore referred to.

It should also be understood that the action of the free-cutting pencil type dressing tool is quite different to that of finish dressing by means of an auxiliary crushing operation or of the usual type of abrasive wheel as the action presents an infinite number of line contacts to the thread of the abrasive wheel as the operation proceeds producing a properly and extremely accurate thread contour and resulting in a highly desirable grain structure on the working surfaces of the thread for the eventual form finishing of gears and similar objects.

This invention may be developed within the scope of the following claims without departing from the essential features of the said invention, and it is desired that the specification and drawing be read as being merely illustrative of a practical embodiment of the same and not in a strictly limiting sense.

It will be understood that, where back lash in transmission is to be contended with, the dressing described may be effected in one longitudinal direction, the dressing tool being withdrawn from contact with the abrasive wheel during its reverse or return stroke such as by the manual means provided and described.

What I claim is:

1. The method of finish forming a helically threaded abrasive wheel of the type described which comprises first roughly forming helicoidal surfaces on said wheel with a crusher wheel contacting therewith and thereafter progressively subjecting the flanks of the wheel thread to the cutting action of a dressing tool of substantially conical form rotating on an axis perpendicular to the axis of said abrasive wheel during rotation of said wheel.

2. The method of finish forming a helically threaded abrasive wheel of the type described which comprises first roughly forming helicoidal surfaces on said wheel with a crusher wheel contacting therewith and thereafter progressively subjecting the flanks of the wheel thread to the cutting action of a dressing tool of free-cutting material and of substantially conical form, said dressing tool being rotated at high speed on an axis perpendicular to the axis of said abrasive Wheel.

3. Means for finish forming a helically threaded abrasive wheel of the type described, said means comprising a rotary dressing tool of free-cutting material and of a substantially coned form in counterpart of the thread spacing, means for rotating said abrasive wheel at a relatively slow speed, means for rotating said dressing tool at a relatively high speed, and said mechanism providing relative motion between said abrasive wheel and said dressing tool whereby said tool will traverse the thread space of said abrasive wheel while maintained perv pendicular to the axis of said abrasive wheel.

4. In a machine for forming a helical thread on the periphery of an abrasive wheel, in combination, a crusher roll, means efiecting relative axial movement between said crusher roll and said abrasive wheel during rotation of said abrasive wheel whereby said roll will crush a thread formation into the periphery of said wheel, a high-speed rotary dressing tool of substantially coned form rotating on an axis perpendicular to the axis of said abrasive wheel and positioned so that its cutting end may enter and traverse the thread space of said wheel upon further relative axial motion of said wheel, and means effecting said further axial motion upon the completion of the initial crushing operation to provide the thread finishing operation by said rotar dressing tool.

FLORYAN A. LOHUTKO.

REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS 

